My guess would be Antioch from deductive reasoning. Antioch is the only city in the original empire, Rome and Corduba are both in the new empire, and Massilia isn't in either empire.
It cannot be Massilia because if your town isn't part of the empire, you wouldn't be under influence of the empire's ruler.
That leaves three answers. Two of which are under the new empire. The only perceivable difference between the remaining three choices in their era. Go with Antioch because it is different from the other remaining two in terms of which empire it belongs too.